Vhf Frequency

Peter A, Stark K20AW 1 96 Forest Drive Ml. Kisco NY 10549

Part 2 of 3 parts

Two months ago we started describing our frequency counter design, showed how to use it; and gave a complete parts list. i his month we will provide the complete logic and schematic diagrams, and describe how it works, and next month we will have the printed circuit board layout, parts layout drawings, and construction and operation information.

Figures 3 through 18 show the diagrams of the various parts of the counter. To see how these parts fit together, refer back to Fig, 2, the block diagram, in last month's article.

0-20 MHz Input Circuit (Fig, 3)

This circuit is one of the most tricky circuits in the counter, since it must convert a variety of input signals, large and small, simple and complex, into digital pulse signals of just the right voltage and speed to operate the counter* This job is considerably simplified by a Sell mitt trigger ft\ an SN74i3\, designed just to interface TTL digital logic to the outside world.

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